Typically, a railcar includes an air conditioning duct which guides conditioned air blowing off from an air conditioner or returns air suctioned to the air conditioner. The air conditioning duct is required to have airtightness and a heat insulating property. Especially, the air conditioning duct of the railcar is also required to satisfy a specific requirement of design, such as flame retardancy or lightness (see PTL 1, for example).
The air conditioning duct disclosed in PTL 1 includes a duct main body and a film member. The duct main body is made of glass wool which is hard to such a degree that the glass wool stands by itself. The duct main body has a square tube shape. The film member has a double-layer structure including an aluminum foil layer and a resin layer and is attached to a surface (an inner surface or an outer surface) of the duct main body. The film member forms one surface of the entire air conditioning duct and blocks the flow of the air from an inside of the duct to an outside of the duct.
Since the duct main body is hard to such a degree that the duct main body stands by itself, shape stability of the entire air conditioning duct can be maintained. Since the duct main body is made of glass wool having sound absorbency and incombustibility, some of the requirements of design of the air conditioning duct can be satisfied. Since the thin film member is attached to the surface of the glass wool duct main body so as to block the flow of the air, a high heat insulating property obtained by a continuous air chamber in the glass wool can be maintained, and condensation can be prevented. In addition, while avoiding an increase in size of the structure, the airtightness of the entire air conditioning duct can be increased. Since the air conditioning duct is constituted by the glass wool duct main body and the thin film member, the air conditioning duct is lighter than an air conditioning duct including a metal duct main body.